// 简化的内存服务实现

use log::info;
use super::{BaseService, ServiceError, ServiceStatus};

// 内存块信息
#[derive(Debug, Clone)]
pub struct MemoryBlock {
    pub address: u64,
    pub size: usize,
    pub used: bool,
    pub permissions: MemoryPermissions,
}

// 内存权限
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MemoryPermissions {
    ReadOnly,
    ReadWrite,
    Execute,
    ExecuteRead,
    ExecuteReadWrite,
}

// 简化的内存服务
pub struct MemoryService {
    blocks: Vec<MemoryBlock>,
    total_memory: usize,
    used_memory: usize,
    status: ServiceStatus,
}

impl MemoryService {
    pub fn new() -> Result<Self, ServiceError> {
        info!("Creating new Memory Service");
        
        Ok(MemoryService {
            blocks: Vec::new(),
            total_memory: 0,
            used_memory: 0,
            status: ServiceStatus::Stopped,
        })
    }
    
    // 初始化内存映射
    pub fn initialize_memory_map(&mut self, total_memory: usize) -> Result<(), ServiceError> {
        if self.status != ServiceStatus::Stopped {
            return Err(ServiceError::MemoryError("Service not stopped".to_string()));
        }
        
        info!("Initializing memory map with {} bytes", total_memory);
        
        self.total_memory = total_memory;
        self.used_memory = 0;
        self.blocks.clear();
        
        // 创建初始内存块
        let initial_block = MemoryBlock {
            address: 0x1000, // 从4KB开始
            size: total_memory - 0x1000,
            used: false,
            permissions: MemoryPermissions::ReadWrite,
        };
        
        self.blocks.push(initial_block);
        info!("Memory map initialized successfully");
        Ok(())
    }
    
    // 分配内存
    pub fn allocate(&mut self, size: usize, permissions: MemoryPermissions) -> Result<u64, ServiceError> {
        if self.status != ServiceStatus::Running {
            return Err(ServiceError::MemoryError("Service not running".to_string()));
        }
        
        if size == 0 {
            return Err(ServiceError::MemoryError("Cannot allocate zero bytes".to_string()));
        }
        
        // 寻找合适的空闲块
        let mut found_index = None;
        for i in 0..self.blocks.len() {
            if !self.blocks[i].used && self.blocks[i].size >= size {
                found_index = Some(i);
                break;
            }
        }
        
        if let Some(i) = found_index {
            let block_address = self.blocks[i].address;
            
            // 如果块大小刚好，直接使用
            if self.blocks[i].size == size {
                self.blocks[i].used = true;
                self.blocks[i].permissions = permissions;
                self.used_memory += size;
                info!("Allocated {} bytes at address 0x{:x}", size, block_address);
                return Ok(block_address);
            }
            
            // 如果块较大，分割使用
            let new_block = MemoryBlock {
                address: block_address + size as u64,
                size: self.blocks[i].size - size,
                used: false,
                permissions: self.blocks[i].permissions,
            };
            
            self.blocks[i].size = size;
            self.blocks[i].used = true;
            self.blocks[i].permissions = permissions;
            
            self.blocks.insert(i + 1, new_block);
            self.used_memory += size;
            
            info!("Allocated {} bytes at address 0x{:x}", size, block_address);
            return Ok(block_address);
        }
        
        Err(ServiceError::MemoryError(format!("Insufficient memory to allocate {} bytes", size)))
    }
    
    // 释放内存
    pub fn deallocate(&mut self, address: u64) -> Result<(), ServiceError> {
        if self.status != ServiceStatus::Running {
            return Err(ServiceError::MemoryError("Service not running".to_string()));
        }
        
        for i in 0..self.blocks.len() {
            if self.blocks[i].address == address && self.blocks[i].used {
                let block = &mut self.blocks[i];
                block.used = false;
                self.used_memory -= block.size;
                
                info!("Deallocated {} bytes at address 0x{:x}", block.size, address);
                
                // 尝试合并相邻的空闲块
                self.merge_free_blocks();
                return Ok(());
            }
        }
        
        Err(ServiceError::MemoryError(format!("No memory block found at address 0x{:x}", address)))
    }
    
    // 合并空闲块
    fn merge_free_blocks(&mut self) {
        let mut i = 0;
        while i < self.blocks.len().saturating_sub(1) {
            let current = &self.blocks[i];
            let next = &self.blocks[i + 1];
            
            if !current.used && !next.used && 
               current.address + current.size as u64 == next.address {
                // 合并块
                let merged_size = current.size + next.size;
                self.blocks[i].size = merged_size;
                self.blocks.remove(i + 1);
            } else {
                i += 1;
            }
        }
    }
    
    // 获取内存使用统计
    pub fn get_stats(&self) -> MemoryStats {
        MemoryStats {
            total_memory: self.total_memory,
            used_memory: self.used_memory,
            free_memory: self.total_memory - self.used_memory,
            block_count: self.blocks.len(),
        }
    }
    
    // 验证内存访问权限
    pub fn validate_access(&self, address: u64, size: usize, required_perms: MemoryPermissions) -> Result<(), ServiceError> {
        for block in &self.blocks {
            if address >= block.address && address + size as u64 <= block.address + block.size as u64 {
                if !block.used {
                    return Err(ServiceError::MemoryError("Accessing unused memory".to_string()));
                }
                
                // 检查权限
                if !self.check_permissions(block.permissions, required_perms) {
                    return Err(ServiceError::MemoryError("Insufficient permissions".to_string()));
                }
                
                return Ok(());
            }
        }
        
        Err(ServiceError::MemoryError("Address not in valid memory range".to_string()))
    }
    
    // 检查权限是否足够
    fn check_permissions(&self, available: MemoryPermissions, required: MemoryPermissions) -> bool {
        match (available, required) {
            (MemoryPermissions::ReadWrite, _) => true,
            (MemoryPermissions::ExecuteReadWrite, _) => true,
            (MemoryPermissions::ReadOnly, MemoryPermissions::ReadOnly) => true,
            (MemoryPermissions::ExecuteRead, MemoryPermissions::Execute) => true,
            (MemoryPermissions::ExecuteRead, MemoryPermissions::ReadOnly) => true,
            (MemoryPermissions::Execute, MemoryPermissions::Execute) => true,
            _ => false,
        }
    }
}

impl BaseService for MemoryService {
    fn start(&mut self) -> Result<(), ServiceError> {
        if self.status == ServiceStatus::Running {
            return Ok(());
        }
        
        info!("Starting Memory Service");
        
        // 初始化默认内存映射（1GB）
        self.initialize_memory_map(1024 * 1024 * 1024)?;
        
        self.status = ServiceStatus::Running;
        info!("Memory Service started successfully");
        Ok(())
    }
    
    fn stop(&mut self) -> Result<(), ServiceError> {
        if self.status == ServiceStatus::Stopped {
            return Ok(());
        }
        
        info!("Stopping Memory Service");
        
        // 释放所有内存块
        for block in &mut self.blocks {
            block.used = false;
        }
        self.used_memory = 0;
        
        self.status = ServiceStatus::Stopped;
        info!("Memory Service stopped");
        Ok(())
    }
    
    fn status(&self) -> ServiceStatus {
        self.status
    }
}

// 内存统计信息
#[derive(Debug, Clone)]
pub struct MemoryStats {
    pub total_memory: usize,
    pub used_memory: usize,
    pub free_memory: usize,
    pub block_count: usize,
}

impl MemoryStats {
    pub fn usage_percentage(&self) -> f64 {
        if self.total_memory == 0 {
            return 0.0;
        }
        (self.used_memory as f64 / self.total_memory as f64) * 100.0
    }
}